The present invention generally relates to brush seals with bristles arranged at an angle. The brush seals may be used for sealing a rotor against a stator in gas turbine engines, for example. More specifically, the present invention relates to brush seals which have a support plate with a longitudinal section and a support section arranged at an angle to the longitudinal section, and bristles with shaft sections and bristle sections arranged at an angle to the shaft sections, with the end of the bristle sections running against the sealing area of the rotor.
Due to various advantages, the use of brush seals in gas turbines is well proven versus other seal designs, such as, for example, lip seals or labyrinth seals.
In German patent document no. 196 18 475 A1, a brush seal is known which has bristles that are arranged at an angle so as to reduce the radial length of the design. In order to keep the greater rigidity of the short bristle sections arranged at an angle, within desirable limits, a limit stop situated in the area of the shaft sections of the bristles has been provided. The limit stop acts as a bending edge if the elastic bristles are subjected to excursion due to rotor eccentricity. In this way, the rigidity of the bristles can be adjusted without requiring the design of an unduly large radial space.
However, leakage occurring with such existing brush seals has proven problematical. The leakage has included a primary leakage through an annular gap between the rotor and the bristle packet on the one hand, and a xe2x80x9cbypass air quantityxe2x80x9d leakage on the other hand, which streams across the bending clearance between the support plate and the bristle packet.
One object of the present invention is to provide improved brush seals with bristles arranged at an angle. It is desirable that an optimal sealing effect is achieved without the so-called xe2x80x9chang-upxe2x80x9d effect occurring in which, in the event of a differential pressure, the bristle packet is pressed against the support plate and remains stuck to the support plate due to frictional force.
According to the invention, the object can be met in that between the shaft sections of the bristles and the support plate, a bending clearance is provided, and between the bristle sections arranged at an angle and across the entire length of the support section of the support plate there is a gap which closes if there is a differential pressure.
One advantage is that, with selection of the gap depending on the differential pressure, the pressure in the bending clearance corresponds to the pressure in front of the brush seal. This means that almost the entire decrease in pressure takes place via the bristle packet arranged at an angle, or the bristle sections arranged at an angle. In the case of pressure being present, the bristle packet is not brought to a constrained position such that it is pressed against the support section with substantial axial pressure, loses its elasticity, and after rotor excursion remains stuck in that position. During normal operation under pressure, i.e. constant operating conditions, the bristle sections arranged at an angle, at least in parts or sections, position themselves against the support section of the support plate while closing the gap.
Preferably, the gap is set such that there are no pressure loads or pressure tensions in the shaft sections of the bristles if there is a differential pressure. Instead, the differential pressure is absorbed as a tensile force in the shaft sections of the bristles. In this way, the pressure in the bending clearance corresponds to the higher pressure in front of the brush seal so that the shaft sections of the bristles do not experience any pressure load and in the case of a change of the pressure level, display a quasi-automatic restoring effect. In the case of a pressure reduction, the temporarily higher pressure in the bending clearance pushes the elastic bristles in the direction of the sealing area of the rotor, i.e. generally, radially towards the interior. Conversely, during an increase in pressure, the shaft sections of the elastic bristles are first lifted way from the sealing surface of the rotor, i.e. generally, radially to the exterior, until pressure compensation takes place.
Preferably, the bending clearance extends up to a rear edge of the longitudinal section of the support plate.
Alternatively, the object can be met in that the bristle sections arranged at an angle are positioned at an angle in the direction of rotation of the rotor, with the angle being between 0xc2x0 and 70xc2x0, for example, between 40xc2x0 and 50xc2x0.
By positioning the bristles in the direction of the rotor, the sealing effect is improved because the air streaming through the bristle packet is deflected by the bristles positioned at an angle. In this way the so-called xe2x80x9cjet-throughxe2x80x9d flow configuration, i.e. channel formation between the row of bristles as it occurs with bristles not positioned at an angle, is avoided. Additionally, during rotor excursions, a large restoring force is generated by the torsion of the shaft sections of the bristles, practically eliminating any adhesion to the support plate, by the bristle sections arranged at an angle.
Preferably, a bending clearance is provided between the shaft sections of the bristles and the support plate, so that the restoring effect of the bristles in the case of changing pressures and excursions of the rotor is generated by concurrent bending and torsion.
Furthermore, it can be advantageous if the shaft sections of the bristles are longer than the bristle sections arranged at an angle, so that the bristle packet, having the restoring effect of the elastic bristles, does not become too rigid.
In an embodiment of the invention, a brush seal with bristles arranged at an angle for sealing a rotor against a stator has a support plate with a longitudinal section and a support section, and bristles with shaft sections and bristle sections arranged at an angle to the shaft sections. The ends of the bristle sections run against the sealing area of the rotor. Between the shaft sections of the bristles and the support plate a bending clearance is provided. Between the bristle sections arranged at an angle and across the entire length of the support section of the support plate there is a gap which closes if there is a differential pressure.
In an embodiment of the invention, the gap of the brush seal is adjusted such that there are no pressure loads in the shaft sections of the bristles if there is a differential pressure.
In an embodiment of the invention, the bending clearance of the brush seal extends to the rear edge of the longitudinal section of the support plate.
In an embodiment of the invention, a brush seal with bristles arranged in an angle for sealing a rotor against a stator has a support plate with a longitudinal section and a support section, and bristles with shaft sections and bristle sections arranged at an angle to the shaft sections. The ends of the bristle sections are lined against the sealing area of the rotor. The brush sections arranged at an angle are positioned at an angle towards the direction of rotation of the rotor.
In an embodiment of the invention, the angle of the brush seal is between 0xc2x0 and 70xc2x0.
In an embodiment of the invention, a bending clearance is provided between the shaft sections of the bristles and the support plate.
In an embodiment of the invention, the shaft sections of the bristles are longer than the bristle sections arranged at an angle.
In an embodiment of the invention, the free ends of the bristles seal against a rotor positioned on the inside.
In an embodiment of the invention, the free ends of the bristles seal against a rotor positioned on the outside.
In an embodiment of the invention, the rotor has a cylindrical annular body.
Objects and advantages of the present invention will become apparent upon reading this disclosure including the appended claims with reference to the accompanying drawings. The objects and advantages may be desired, but are not necessarily required, to practice the present invention.